A Thai Army soldier stands guard at Government House, where the anti-government protesters had setup their main camp in Bangkok on May 23, 2014 a day after Thai military seized power.

History of instability

Thailand has a history of political instability with over 20 prime ministers since 1946 when a new constitution came into being. It has faced 19 military coups, 12 successful, since the country became a constitutional monarchy in 1932.

Thursday's coup followed over six months of political protests amid a power struggle between supporters of former Prime Minister Thaksin Shinawatra and the royalist establishment.

The last time the military intervened was in 2006 to oust Thaksin. The military held control for more than a year until elections were help in December 2007.

On the one hand is the "red-shirt" faction. It supports Thaksin and his sister Yingluck Shinawatra who was ordered by the courts to step down as prime minister on May 7 for an abuse of power. The red shirts say the 2006 coup and subsequent court rulings that dissolved parties close to Thaksin show that Thai society is unjust.

Then there is the "yellow shirt" faction. This is made up of the middle class in Bangkok, the Thai capital, royalists and retired generals. They have called for several versions of an appointed government in recent months and are aligned to the opposition Democrats, who have not won a national vote since 1992 and boycotted an election in February.

Army chief Prayuth Chan-ocha, who declared martial law on Tuesday, had tried to get various factions to talk before Thursday's bloodless coup.

Violence?

The red shirts took to the streets in 2009 and 2010 to call for fresh elections and the fear is they will do the same again. The 2010 protests were put down by the military and resulted in more than 90 deaths.

According to a Reuters report on Friday, the red-shirt supporters said they had no immediate plans for protests that they had threatened should the army seize power.

Still, analysts do not rule out large-scale protests that could descend into violence.

"The Red Shirts now appear to have the capacity not only to bring large-scale protests to the streets but also, we believe, to pursue a serious insurgency from its heartlands in the north of the country," Nomura said in a note Thursday.

King Bhumibol Adulyadej has headed Thailand's constitutional monarchy for over 60 years, but the 86-year-old's health is failing. While he is revered across the country and seen a source of stability, there are concerns about the future.

"The 500-pound gorilla in the room is the health of the king, how long he'll be around and who will follow," Steve Vickers, CEO of Steve Vickers & Associates, a risk mitigation consultancy, told CNBC.

Army chief Prayuth Chan-ocha was expected to meet the king on Friday to explain the army's move.

International response

The coup has been condemned by a number of countries including the U.S., the European Union and Thailand's neighbors in Asia -- Japan and Australia.

Countries such as the U.K. and Singapore meanwhile have issued travel warnings to citizens traveling to or in Thailand.

Kristie Kenney, U.S. ambassador to Thailand, told CNBC: "The safety of U.S. citizens is my top priority and the top priority of our embassy."

"We have advised U.S. citizens of the coup, of the curfew which is 10pm to 5am throughout Thailand and we have asked them to use caution," she added.